Safety device for the prevention of overloading cranes and the like



Oct. 1, 1935.- L. B. N EAL Er AL 2,015,957

SAFETY DEVICE FOR THE PREVENTION OF OVERLOADING CRANES AND THE LIKE v 2Sheets-Sheet 1' Filed Dec. 23, 1930 INVENTORS .l u'l'e 2117.240 andfltaw M Sta mar ATTORN EY Oct. 1, 1935. L. B. NEAL El AL SAFETY DEVICEFOR THE PREVENTION OF OVERLOADING CRANES AND THE LIKE Filed D60. 23,1930 2 Sheets-Sheet 2 VIII/ll fill/Ill KW q ELK M b j WITNESS d/ ATTOR NEY Patented Oct. 1, 1935 UNITED STATES PATENT OFFICE SAFETY DEVICE FORTHE PREVENTION OF OVERLOADING CRANES AND THE, LIKE Lillie B. Neal andBlanche M. Stoner, Bremerton, Wash., assignors to J. 0. Neal, PortOrchard,

Wash.

Application December 23, 1930, Serial No. 504,384

6 Claims.

and claimed.

It is an object of our invention tov provide a safety device for cranesand the like wherein an operator of the crane may be appraised of theload upon the crane, thus avoiding accidents due to an overloading ofthe crane, which in many instances causes overturning thereof.

'It is a further object of the invention to provide a safety device inwhich a visual indicator is employed, operable in conjunction with anaudible signal.

A still further object of the invention is the provision of a safetydevice wherein a warning of load limit will be given at any danger pointof the radial swing of the boom. I

Additional objects, advantages and features of invention will beapparent from the following description and accompanying drawingsforming a.- part of this application, wherein,

Figure l is a side elevation of a locomotive crane equipped with onesafety device,

Figure 2 is a top plan view of the boom,

Figure 3 is a plan view of the indicator,

Figure 4 is a vertical section of the indicator and illustrating theelectrical circuit for the audible signal,

Figure 5 is an enlarged vertical section on the line 5--5 of Fig. 3,illustrating the operating mechanism for the indicator, and

Figure 6 is a detail of one of the drums.

. It will beunderstood that we do not limit ourselves to the adaptationof our device to locomotive cranes, but, for illustration, we have shownthe invention as applied to a locomotive crane ill, which may be of anyusual construction embodying a boom II. The boom II is suitably mountedfor vertical swinging movement as at l2, and movable radially with thecabin l3, as is customary.

The crane l0 embodies a power drum I4 having a load line l5 threadedthrough a sheave l6 mounted at the outermost point of the boom H andthrough block H from whence the cable is passed around a sheave l8. Fromthis sheave, the cable I5 is extended rearwardly and trained about apulley i 9 carried upon a lever mounted adjacent the base of,the boomII, as clearly shown in Fig. 2. After passing through the pulley t9, thecable is extended forwardly for passage around a pulley 21, mounted uponthe forward end of the boom H, but to the rear of the sheaves 16 and I8.The cable I5 is finally secured to the block ll as at 22. It is evidentthat the particular arrangement of the cable 15 from the power drum l4to its dead end, as above described and shown,

have no relation to this invention and that that 5' portion between thepulley l9 and the shackle 22 may be considered the deadend of the cable.The stress on the ,cable I5 is, of course, the same at all pointstherein and depends on the weight lifted and the number ofcable-sections supporting the block H. In the drawings this stress istherefore one-third of the weight being lifted, but if the dead end wereloosed from the block I1 and attached. directly to the lever 20, thestress therein would be one-half that of the weight, while if it passedtwice around the pulleys in the block I! and the end of the boom andthence to the lever 20, the stress therein would be one-quarter that ofthe weight.

From a consideration of Fig. 2, it will be noted 20 that the lever 20 ispivotally mounted upon one side of the boom II, as indicated at 23, andadjacent the opposite end is suitably apertured for mounting of acompression spring 24. The spring is confined within a suitable housingwhich is secured by a. tum-buckle or other suitable adjusting device 25to the base of the crane Ill. The tension of the spring may thus bevaried by adjustment through the turn-buckle.

The lever 20 may be apertured as at 26 in order to vary the attachmentof the pulley l9, as found necessary, thereby varying the proportion ofthe stress, in the weight-raising cable I5, which is counterbalanced bythe spring 24 and therefore varying the extent of movement of the lever20 for a given load on the crane boom.

A cable 21 is attached to the lever 20 adjacent its free end and passestherefrom under the pulley 28, adjacent the pivot pin E2 of the boom,and thence around suitable pulleys 28 to our indicator 29, which will befully described hereinafter. A cable 30 extends from our indicator,suitably guided by pulleys 3| and is attached to the boom H as at 32. Wepreferably include adjusting means 33 in the cables 21 and 30 to take upany slack which may occur through stretching, or otherwise.

From the foregoing, it will be apparent that as the weight is applied tothe power line IS, a pull will be exerted upon the cable 21; and thatany raising movement of the boom II will cause a correspondingslackening movement to the cable 30 and vice versa.

Our indicator 29 is mounted within the cabin 13 in a positionimmediately before an operator of the crane, and in our presentconstruction embodies a housing ll having a shaft 35 Journalled in theupper part thereof. A cam or drum I6 is keyed upon the shaft 38 and ispreferably ecoentrlcally mounted with respect to the shaft. so that anyvariation in the travel of the boom H may be readily accommodated. Thedrum It is suitably grooved to receive the cable 21, the end of which issecured therein.

A drum I1 is also keyed upon the shaft II, and has a cable It coiledtherearound to the lower end of which there is secured a counterweight19. adapted to keep the cable I! taut.

As clearly shown in Fig. 5, a hollow shaft 40 is revolubly mounted onthe shaft 35 and has keyed thereon drums II and 4!. The shaft 40projects through the housing II at one side but stops short of theprojecting end 35a of the shaft 3!. Indicator hands 48 and II aresecured upon the projecting ends of respective shafts l and 40 forrotary movement about the dials Cl and it, respectively, caused byrotation of respective drums 80 and I2.

Becured to the drum ll, we provide a cable I], to the lower end of whichthere is attached a counterweight 4' adapted to keep the cable It taut.

The counterweights II and 4B are movable longitudinally of the housingII, and are suitably guided in their paths by a guide-way 09.

The cable ll is coiled about the drum 4! and the end thereof secured tothe drum in a suitable manner.

It will be apparent that a pull upon either of the cables 21 or II willcause rotation of its associated drum, and consequent movement of theindicator hands ll or 44, as the case may be. It is also apparent. sincean increase in the weight lifted causes a tension in the cable 21 and acounterclockwise rotation of the shaft 3! and its indicator hand 43, anda raising of the counterweight and an increase in the leverage of theweight or the distance that the boom end extends from the cabin IIcauses a slackening of the cable SI and consequently a clockwiserotation of the shaft II and its indicator hand 44, and a lowering ofthe counterweight ll, that the hands 48 and ll turn in oppositedirections on an increase of either the weight or its leverage, and thatthe counterweights 38 and 48 also travel in opposite directions on suchincrease. When the crane is inactive and the boom is raised, thecounterweight II is at the top of its travel and the counterweight II isat its lowest point of travel. when the combined effect of an increasein the weight and/or leverage is such as to endanger the safety of thecrane, the said counterweights will have moved to the relative positionsshown in Fig. 4, though it must be understood that this condition mayoccur at any point in the travel of the weights, for instance, anextremely heavy weight will cause the counterweights 39 and ll to meetat the upper end of their travel, thus indicating that the boom must beheld substantially vertically when handling such a load, while acomparatively light load will cause them to meet at the lower end oftravel when the boom is extended as low as possible. The crane can besafely handled so long as the counterweight l! is higher than the weight38, but any increment of added weight or leverage will immediately bringthem into line.

To provide an audible signal, we mount a pair of contracts III and Iiupon the counterweights II and I. These contacts are suitably insulatedand of a length to aflord a brushing contact one with the other, duringmovement of the counterweights. An electric bell I2, and battery 88 isin electrical connection with the contacts 50 and II so that the bellwill be sounded upon completion 5 of the circuit through movement of thecounterweight.

The operation of our device is substantially as follows:

We will say that we are about to elevate an object twenty feet away fromthe center of gravity of the crane, and the load limit at this radius is10 tons. The movement of the boom I l to position to bring the block Hto a point centrally of the object to be elevated will cause a move- 16ment of the cable It, and in doing so rotation of the drum 4! iseffected, with consequent movement of the indicator hand 44 on the dial4. to indicate. the movement of the boom. During movement of the drum4!, a like movement is imparted to the drum II, which in turn moves thecounterweight ll to a predetermined point. Now, if the object to belifted does not exceed the permissible 10 tons the crane may beoperated, as usual through the power drum ll. Also the pull exertedthrough the power line II will pull the lever 20 compressing the spring24, and pulling the cable 11. The pull upon the cable 21 causes rotationof the drum It and rotation of the hand 43 to indicate the weight beinglifted. However, should the weight exceed the assumed .10 tons, the handll will turn until it assumes a position directly over the hand I. Themovement of the hand 43 has also brought the counterweight 39 directlyopposite the counterweightl8, and therefore the contacts are incontacting relation one with the other, consequently sounding the bellI2, to indicate an excessive load and return of the boom to thevertical.

Upon release of a load, the hands I! and N 40 will assume their normalzero reading. brought back to such position through the counterweightsl9 and It. It should also be noted that the hands 43 and 4| aresynchronized with the contacts 50- carried by the counterweights.

From the foregoing it will be apparent that we have provided a safetydevice which is simple in construction and efficient in operation, andone which may be readily installed upon cranes already in use.

What is claimed is:

l. A safety device for cranes comprising a swinging boom; aweight-raising cable therefor; an indicator having a pair of concentricdials; a pair of indicator hands mounted in the axis of said dials andadapted to indicate, respectively, the

radius of said boom and the weight being raised by said cable; a shaftfor each of said hands; cable means connected between said boom and oneof said shafts; means mounted on said boom and connected to saidweight-raising cable and movable thereby in response to the load appliedthereto; cable means connected between said other shaft and saidload-responsive means; and counterweights operably connected with saidlast two cables whereby said cables are maintained taut.

2. A safety device for cranes comprising a vertically swinging boom; aweight-raising cable therefor: an indicator having a pair of concentricdials; a pair of indicator hands mounted in the axis of said dials andadapted to indicate, respectively, the radius of said boom and theweight being raised by said cable; a shaft for each of said hands, cablemeans connected betact witheach other and in circuit with an elect'ricsignal whereby said signal will be energized upon mutual contacting ofsaid contacts during movementof said counterweights.

' 3. A safety device for cranes or the like, comprising a verticallyswinging boom; a lever pivoted at one end to said boom andextendingtransversely thereof; a weight-raising line, wholly independent in itsoperation of the operation of said vertically swinging boom. and havingitszdead end connected with said lever and having the weightraisingforce applied to its other end; a counterbalancing spring between saidlever and said boom; an indicator; a pair of rotatable hands; and cablemeans between the respective hands and said lever and boom, whereby saidhands are rotated in opposite directions to indicate respectively anincrease in the radius of said boom and the weight applied to saidweight-raising line.

4. A safety device for cranes having a means for raisinga weight atvariable radii'from the center of gravity of the crane, and independentmeans forchanging the said radius an indicator; a pair of concentricshafts mounted therein and each carrying an indicator hand; a pair ofoperating drums mounted on said concentric shafts; cables wound on bothsaid'drums and operatively connected respectively .to the weight-raisingmeans and to the radius-changing means, whereby an increase in bothsaidmeans will cause the .corresponding drums to rotate in oppositedirections; a second pair of drums mounted on said concentric shafts;cables woundon said second pair of drums in directions opposite to thedirections of I the cables wound on the first pair of drums on the sameshafts. respectively; and counterweights onsakisecondpairofcabless- 5. Asafety device for cranes having a means for raising a weight at variablethe center of gravity of the crane, andindependent means for changingthe said radius; an indicator;

a pair of concentric shafts mounted therein and g each carrying anindicator hand; a pair of operating drums mounted on said concentricshafts; cables wound on both said drums and operatively connectedrespectively to the weight-raising means and to the radius-changingmeans, where- '10.

by. an increase in both said means will cause the corresponding drums torotate in opposite directions; a pair of counterweights; and connectingmeans between said counterweights and said concentric shafts wherebysaid counterweights tend to oppose the motion of the respective shaftsunder the action of said weight-raising means and said radius-changingmeans.

6. A safety device for cranes having a means. for raising a weight atvariable radii from thecenter of gravity of the crane, and independentmeans for changing the said radius; an indicator;

a pair of concentric shaftsmounted therein and each carrying anindicator hand; a pair of operating drums mounted on said concentricshafts; cables wound on both said drums and operatively connectedrespectively to the weight-raising means and to the radius-changingmeans, whereby an increase in both said means will cause thecorresponding drums to rotate in opposite directions; a pair ofcounter-weights; connecting means between said counterweights and saidconcentric shafts whereby said counterweights tend to oppose the motionof the respective shafts under the action of said weight-raising meansand I said radius-changing means; an electric signal circuit; and a pairof electric contacts mounted in the signal circuit and operativelyattached to the respective counterweights and adapted to move therewithinto contact with each other to close so the signal circuit when thecombined action of the weight lifted and the radius of action thereofexceeds a predetermined amount.

IJLLIEB. NEAL.

